The present invention relates to a star sensor arrangement for a satellite which on its orbit and/or during the transfer into the orbit rotates at least with a part about an axis of rotation fixed with respect to the satellite, and which is equipped with a star sensor looking in the direction of the axis of rotation and likewise rotating about the axis of rotation.
Such a star sensor arrangement is known from German patent application No. P 34 28 741.8 (U.S. Pat. No. 4,674,715). What is involved there is an earth satellite which comprises a satellite body oriented toward the sun as well as a functional part rotatably connected therewith. The functional part carries functional elements oriented toward the earth, for example, antennas or cameras. During one orbital revolution about an axis of rotation oriented perpendicularly to the orbital plane and fixed with respect to the satellite, it executes almost a complete rotation in the orbital direction. Applied on the functional part is a star sensor viewing in the direction of this axis of rotation, as is also an additional star sensor, but which has a viewing direction which differs from the axis of rotation and which due to the rotation of the functional part revolves quasi on a conical generated surface with the axis of rotation as the axis of symmetry.
By means of the two star sensors provided on the rotating functional part this known measuring arrangement can provide a very accurate position determination of the functional part itself, the exact orientation of which is of primary importance.
However, it appears as a disadvantage that two star sensors must be used. These components are relatively expensive, and it is therefore desirable to reduce their number as far as possible.
Also spin-stabilized satellites, which as a whole rotate relatively fast about an axis of rotation generally fixed in space, may be equipped with one or more star sensors, at least one of which is oriented with its viewing direction in the direction of the axis of rotation. If only one such star sensor is provided, difficulties may arise with such a satellite, for example, in the transfer phase before the desired orbit is reached, due to the fact that the one star sensor, which generally looks in the thrust direction, temporarily does not have a bright star in its field of vision. Thereby even a rough position control during the transfer phase is rendered difficult at best.